A gyroscope flight instrument is a disk, or wheel, mounted on an instrument that is designed to measure angular velocity by utilizing the principle of gyroscopic inertia. Once the wheel has been accelerated, its inertia keeps the disc stable about its axis of rotation. When the instrument is level in flight, a deviation in flight path will move the gyroscopic wheel in its gimbal mount. This movement is then translated to a needle, or card, on the instruments face. Pilots use a gyroscopic attitude indicator, a directional gyroscope, and turn indicators for navigation purposes.